In some cases, a process of forming a thin film, such as a silicon oxide (SiO) film or a silicon nitride (SiN) film, on a substrate may be performed as a process included in a process of manufacturing a semiconductor device. The silicon oxide (SiO) film has high insulating properties and low dielectric properties and is thus widely used as an insulating film or an interlayer film. In addition, the silicon nitride (SiN) film has high insulating properties, high corrosion resistance, low dielectric properties, high film stress controllability, etc., and is thus widely used as an insulating film, a mask film, a charge accumulating film, or a stress control film. In addition, a technique of forming a thin film, such as a silicon carbonitride (SiCN) film, a silicon oxycarbonitride (SiOCN) film, a silicon oxycarbide (SiOC) film, or a silicon boron carbonitride (SiBCN) film, by adding carbon (C) and/or boron (B) to the silicon oxide (SiO) film and the silicon nitride (SiN) film has been known. An etching resistance of a thin film may be enhanced by adding carbon (C) thereto.